Ester type surface active agents



2,898,352 Patented Aug. 4, 1959 ESTER TYPE SURFACE ACTIVE AGENTS No Drawing. Application July 29, 1957 Serial No. 674,576

'5 Claims. (Cl. 260400) This proposal relates to a new method for the-preparation in a practical and economical manner of synthetic detergents of the class of esters of a fatty acid and a hydroxy alkane sulfonic acid and compositions of matter containing such synthetic detergents. More particularly, the present invention is directed to a novel method for the preparation of synthetic detergents by the reaction ofv a mixed anhydride of a fatty acid and boric acid with water soluble salts of hydrox-yalkane sulfonic acids, with the formation of one mole of boric acid for each three moles of ester produced. The novel reaction thus described is considered to be represented by the following wherein n represents an integer of 2 or more preferably 2 to 4, and R, R and R" represent acyl groups of identical or dissimilar numbers of carbon atoms, including caproyl, lauroyl, myristoyl, palmitoyl, stearoyl, undecylenoyl, olcoyl, lineleoyl, and other fatty acids containing eight or more carbon atoms in their chain, or the acyl residue of a cycloalkane carboxylic acid or phenyl acetic acid of an aromatic acid such as benzoic acid, toluic acid, cumic acid and preferably higher alkyl benzoic acid such as otyl benzoic acid, nonyl benzoic acid, dodecyl benzoic acid, or of a naphthoic acid such as a or ,6 naphthoic acid or of an alkylbenzoic acid, and R' and R represent alkyl groups or hydrogen, and X represents a salt forming cation e.g. calcium, magnesium and particularly the alkali metals (especially sodium and potassium) or a tertiary amine group suchas the salt of N-N-diphenylmethylamine, trioctylarnine, N N dimethyloctadecylamine, and N-N-dihexylmethyl amine. r

' The reaction of higher fatty acids with hydroxyalkane sulfonic acids to yield anionic surface active materials useful as wetting, cleansing, softening and dispersing agents is well known. In U.S. Patent 2,635,103 (E. F. Drew & Co., Inc., N.Y., N.Y.) there is disclosed the reaction of one mole of a water soluble hydroxyethylsulfonic acid salt with less than one and more than 0.6 mole of fatty acid at temperatures of ZOO-300 C. at subatmospheric pressures for a sufiicient period of time, considered as four hours or more to complete the reaction. Precautions are given to maintain an inert atmosphere with nitrogen or carbon dioxide to provide maximum assurance of a light colored product when subjecting these intermediates to prolonged high temperatureconditions.

In PB Report #70344, Textilhilfsmittel-Kommission Scientific Exchange Hoechst No..154. Register No. 043/4 information is disclosed that'thesynthesis of surface describedand boric acid with a hydroxyalkane su1fonic 2 active agents by the direct esterification of free fatty acids and hydroxyethylsulfuric acid salts is of great commercial significance. The report notes the preparation. of the intermediate fatty acid chloride would be eliminated by this direct procedure, and the phosphorus trichloride required for the intermediate acid chloride step would be saved. Furthermore, the report states that a fatty acid and a hydroxyethane sulfonic acid salt can be condensed by heating to about 220 C., the dehydration starting slowly at this temperature. Dr. Frank, the author of the report, states the condensation was initially performed under addition of catalysts, especially of acid character. However, he states all these compounds have an unfavorable effect with regard to the color of the products obtained. The report recommends temperatures of 250260 C. or higher with the best possible vacuum to complete the dehydration.

In U.S. application Serial No. 470,500 of R. L. Sundberg, there is described the condensation of sodium isethionate with stearic acid at 240-25 0 C. using boric acid as a catalyst.

r In U.S. application Serial No. 603,214 of R. J. Ander son and L. M. Schenck, there is disclosed that the reaction rate of a higher fatty acid, including stearic acid, oleic acid, lauric acid, coconut acid, and other aliphatic acids containing eight or more carbon atoms in their chain and a hydroxyalkane sulfonic acid salt, including the sodium or potassium salt of isethionic acid, can be accelerated if the pH range of the reaction mixture is maintained below pH 5 by the addition of an acidic catalyst. The preferred range is pH 2.8-pH 3.2, but this range is not to be considered as a limit to the scope of the invention. The preferred catalyst is an aqueous acidic phosphorus compound, introduced as 2.0-2.2% by weight as phosphoric acid to the molten fatty acid. However, other acidic catalysts or catalyst combinations providing the desired pH range may be employed.

Contrary to expectations, I have found that the same ester-type detergents from higher fatty acids and hydroxyalkane sulfuric acid salts can be formed at temperatures as low as normal room temperatures without resorting to the use of fatty acid chlorides, and completely apart from the drastic thermal conditions described in other disclosures whereby various catalysts of an acidic nature are described. In spite of the teachings of Conk, Ilett, Saunders and Stacey, J. Chem. Soc., 3125, 1950, who state In general, heating triacetate (boron) with an alcohol gave the corresponding ester of boric acid, and the work of Pictet, Ber., 36, 2219 (1903). l

I have found that higher molecular weight mixed anhydrides of carboxylic acids and boric acid react with alcohol substituents as exemplified by sodium isethionate to yield not the anticipated boron ester of the alcohol but the fatty acid ester of the hydroxyalkane sulfuric acid salt.

An obvious advantage and object of my invention is its ability to operate at temperatures substantially lower than those disclosed by the prior art. Since the reactants employed are subject to thermal decomposition when maintained at elevated temperatures for prolonged periods of time, and since equipment suitable for the high temperature reactions disclosed in prior art is expensive to install and maintain, my invention will allow those skilled in the arts to employ a process not only more economically feasible from an equipment standpoint but also one which provides advantages of product purity by prevention of thermal decomposition of the reactants employed. Further advantages and objects of my invention will be apparent as the present description progresses.

In brief, the process of the present invention comprises reacting a mixed anhydride of carboxylic acid of the type acid. This reaction will proceed to some extent at room temperature. However, for ease of manipulation and also to speed up the reaction, a temperature in the range of 50 C. to 150 C. is to be preferred, since within these temperature ranges the fatty acid intermediate is in a liquid form thus lessening'the mechanical problems encountered in mixing the desired reactants and obviating any need to employ inert liquid diluents or solvent although the reaction is operable in the presence of an inert solvent. For best results, it is also advisable that moisture be rigidly excluded from the reaction since the mixed anhydride of boric acids and the fatty acids are readily hydrolizcd to boric acid and free fatty acid by reaction with water.

Suitable methods for the preparationof the mixed fatty acid-boric acid anhydrides employed as acylating agents in the process of this invention are known in the art. Such mixed anhydrides were apparently prepared first by Pictet, Berichte, 36, 2212 (1903), namely from boric acid and carboxylic acid anhydrides (1) Dimroth, Annalen, 446, 97 (1926); Berichte, 54, 3029 (1921), and Cook et al., J. Chem. Soc., 3125.

(2) Boric acid and carboxylic acid chlorides (see also Brooks, J.A.C.S., 34, 492 (1912)).

(3) By acidolysis.

Among others Pictet prepared mixed anhydrides of boric acid and stearic acid. A preferred method of synthesis of the mixed boric acid higher fatty acid anhydride is disclosed in detail in the accompanying examples and involves first the preparation of the boron triacetate by reaction of three molar proportions of acetic anhydride with boric acid followed by the reaction of the thus produced boron triacetate with stearic acid and then distilling off under reduced pressure the acetic acid and any excess acetic anhydride. Among the higher fatty acids whose mixed anhydrides with boric acid can be used in practicing the present invention may be mentioned caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, undecylenic acid, abietic acid, and particularly mixtures of the same such as the mixtures of fatty' acids obtained from natural fats and waxes such as coconut oil fatty acids, tallow fatty acids, tall oil acids, or fatty acids of synthetic origin, such as those obtained by partial oxidation of higher boiling petroleum fractions, acids from oxo acids and aldehydes etc. Similarly the mixed anhydrides of boric acid and cycloalkyl or aromatic carboxylic acids of the type previously mentioned may be prepared and used in practicing the present invention.

As examples of hydroxyalkane sulfonic acids which may be employed in the present invention may be mentioned especially isethionic acid, although other hydroxyalkane sulfonic acids of the general formula indicated above may be employed if desired and may in fact be preferable for certain specific types of compositions. As examples of such other hydroxyalkane sulfonic acids may be mentioned 2-hydroxypropanesulfonic acid, 2-hydroxy-3-butane-sulfonic acid, 2-hydroxy-1-butane sulfonic acid.

The details of the present invention will be apparent to those skilled in the art from a consideration of the following specific examples describing preferred embodiments of the invention. In these examples where methylene blue analysis is referred to there is meant the method for determining the percent of fatty acid esters described in Nature, 160, 759 (1947), and Trans. Faraday Soc.,-44, 226-239 (1948).

Example 1 Charge into a one liter flask equipped with an efiicient the formation of boron triacetate, add 144 g. (0.534 v mole) commercial stearic acid. Warm to 100 C. for two hours, then distill off under reduced pressure the acetic acid formed and any excess acetic anhydride. The

total weight of the distillate varies from 70-80 g. Add

4 to the crude borontristearate 52.5 g. sodium isethionate (0.354 mole). Heat at 125 C. for twenty hours. A weighed sample at this point shows the reaction product contains 57.2% of a stearic acid ester of sodium isethionate by methylene blue analysis. The detergent mixture foams freely in water, and exhibits excellent detergent properties. As a control, a mixture of 144 g. (0.534

mole) commercial stearic acid 52.5 g. (0.354 mole) sodium isethionate and 11.0 g. (0.178 mole) boric acid were heated twenty hours at 125 C. to give a reaction mixture containing only 3.9% of a stearic acid ester of sodium isethionate by the same analysis. As an additional control, 66.7 g. (0.664 mole) acetic anhydride 144 g. (0.534 mole) commercial stearic acid were heated at C. one hour, then 135 C. one hour, and the volatile component removed by vacuum distillation. There was added to the fatty acid residue 57.5 g. (0.388 mole) sodium isethionate, and the reaction mixture heated at C. for twenty hours. The mixture on analysis showed only a 2.8% content of the stearic acid ester of sodium isethionate.

Example 2 Example 3 Following the method given in Example 1, 66.7 g. acetic anhydride (0.664 mole) is reacted with 11.0 g. (0.178 mole) boric acid. Without isolation of the boron triacetate, there is added 116 g. coco fatty acid (0.546 mole, M.W. 212). After warming to convert the coco fatty acid to the mixed anhydride with boric acid, the liberated acetic acid is distilled off in vacuo, and there is added 52.5 g. (0.354 mole) sodium isethionate. The reaction mixture is heated at C. eleven hours to produce a reaction mass analyzing 55.5% as the ester of sodium isethionate of coco fatty acid. The product shows good detergency in washing tests. As a control, a mixture of 116 g. coco fatty acid (0.546 mole), 11.0 g. (0.178 mole) boric acid and 52.5 g. (0.354 mole) sodium isethionate were heated eleven hours at 130 C. The product thus obtained only analyzed 8.15% as the coco fatty acid ester of sodium isethionate.

Example 4 In a manner comparable to that used in Example #1, the mixed anhydride of tallow fatty acid and boric acid was prepared from 66.7 g. (0.664 mole) acetic anhydride 11.0 g. (0.178 mole) boric acid and 152 g. tallow fatty acid (0.534 mole, M.W. 285). Following removal of acetic acid and acetic anhydride, there was added to the mixed tallow fatty acid-boric acid anhydride 52.5 g. sodium isethionate (0.354 mole). The reaction was heated at 125 C. four hours to give a crude product analyzing 18.3% of the desired tallow fatty acid ester of sodium isethionate. In contrast, a control experiment using 152 g. tallow fatty acid (0.534 mole) 52.5 g. sodium isethionate (0.354 mole) and 11 g. boric acid (0.178 mole) heated at 125 C. four hours yielded 0.00% tallow fatty acid ester of sodium isethionate.

Example 5 ing heating at C. three hours there is obtained a) detergent mixture analyzing as 84% stearic acid ester of sodium isethionate, with the anticipated detergent properties.

Example 6 Boron triacetate is formed from 66.7 g. (0.664 mole) acetic anhydride and 11.0 (0.178 mole) boric acid as outlined in Example 1. The mixed acetic acid-boric acid anhydride is reacted in situ with 144 g. (0.534 mole, M.W. 270) commercial stearic acid. Following removal of the acetic acid by atmospheric distillation, the residual crude mixed anhydride of stearic acid and boric acid is heated with 57.5 g. (0.354 mole) sodium-B-methylisenthionate at 125 C. for four hours. At the end of four hours, the reaction mixture analyzed as 40.6% of the stearic acid ester of sodium-B-methylisethionate, and exhibited interesting detergent properties.

A control experiment in which a mixture of 144 g. (0.534 mole) stearic acid, 57.5 g. (0.354 mole) sodium- B-methyl-isenthionate and 11 g. (0.178 mole) boric acid were heated four hours at 125 C. analyzed as 2.3% stearic acid ester of sodium-B-methylisethionate.

Example 7 Employing the same procedure and molar ratio of reactants as given in Example 3 for the preparation of the mixed anhydride of coco fatty acid and boric acid, sodium isethionate was reacted for two hours with the residual coco fatty acid-boric acid mixed anhydride at 50 C. to yield a crude product analyzing as 12.2% coco fatty acid ester of sodium isethionate.

It will be apparent from the consideration of the foregoing examples that for most detergent applications, the production of a pure fatty acid ester of sodium isethionate is not essential, and from an economical standpoint, a product comprising a final mixture of fatty acid soap and fatty acid ester of sodium isethionate is normally preferred and the presence in such mixture of borax is not objectionable. However, if desired, the borax and the sodium isethionate may be removed from the product by suitable methods such as filtration of the molten product, or solvent extraction with either organic solvents such as hydrocarbons, alcohols or esters to remove the fatty acid isethionic acid esters from the borax and sodium isethionate or aqueous extractions to remove the more soluble borax and sodium isethionate from the desired product. The relative proportions of fatty acid soap and fatty acid ester of sodium isethionate desired in the final product will be determined primarily by economic considerations and the specific applications for which the detergent is intended. The presence of as little as 10% of sodium isethionate in the final detergent substantially improves the performance of soap, particularly from the standpoint of preventing the precipitation of curds of alkaline earth metal or other heavy metal soaps in hard Waters.

While the present invention has been described in specific detail in connection with the preparation of esters of higher fatty acids with isethionic acid, since these represent a preferred embodiment of the invention, and the product thus obtained is a preferred type of surface active agent for the production of which the present process is of particular value, it will be understood that as previously mentioned the process of this invention is of general applicability to the production of esters by reaction of hydroxyalkane sulfonic acids with mixed anhydrides of boric acid and carboxylic acids of the type whose esters with hydroxyalkane sulfonic acids have heretofore been suggested as surface active agents. Thus in place of sodium (or other salt of the type included) isethionic there may be employed other hydroxyalkane sulfonic acids whose esters of fatty or other carboxylic acids have been suggested as surface active agents. Similarly in place of the specific fatty acids employed in the foregoing examples,

other higher fatty acids may be employed as esters with isethionic acid or other hydroxyalkane sulfonic acids have been suggested as surface active agents where in place of mixed anhydrides of boric acid with higher fatty acids there may be employed the mixed esters of boric acid with cycloalkane carboxylic acids or benzoic acids preferably alkyl substituted benzoic acids whose esters with isethionic (or other hydroxyalkane sulfonic acids) are known to have surface active properties.

I claim:

1. A process of preparing ester type anionic surface active agents which comprises reacting a mixed anhydride of a fatty acid containing at least 8 carbon atoms and boric acid with a water-soluble salt of a monohydroxyalkane monosulfonic acid.

2. The process as defined in claim 1, wherein the hydroxyalkane sulfonic acid is an alkali metal salt of isethionic acid.

3. The process as defined in claim 2, wherein the alkali metal salt of isethionic acid is sodium isethionate.

4. The process as defined in claim 2, wherein the alkali metal salt of isethionic acid is potassium isethionate.

5. A process of preparing anionic surface active agents which are esters of a carboxylic acid and a hydroxyalkane sulfonic acid which comprises reacting a mixed anhydride of boric acid and the carboxylic acid corresponding to the carboxylic acid moiety of the anionic surface active agent with a water soluble salt of a mono-hydroxyalkane monosulfonic acid.

References Cited in the file of this patent Richter: Textbook of Organic Chemistry (1938), p. 183, John Wiley & Sons, New York.

UNITED STATES PATENT OFFICE @ERTIFICATE OF CORRECTION Patent No. 2,898,352 August 4, 1959 Leslie Millard Schenck It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent. should read as "corrected below.

Column 1, line 40, for "olcoyl, lineleoyl" read oleoyl, linoleoyl same column 1, line 45 for 'fotyl" read actyl Signed and sealed this 19th day of December 1961 Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC- 

